36 The Carboniferous Formation, 



Saturday, March ^Sth, 1868. 



The Forty-second Meeting of the Society was held at the Presi- 

 dent's House. 



Clarke and Dunn were elected members. 



The exhibitions were : — 



Some Coal Fossils, sent by Mr. Griffith, to illustrate the Paper read by 



Balfour, upon " The Carboniferous Formation." 

 Some Fossil Coal Calamites, &c., and Fish Remains . . By Balfouk. 



Balfour then read a Paper on 



THE CARBONIFEROUS FORMATION. 



The carboniferous formation, or coal, may be divided into two 

 sections. 1. The coal measures, consisting of alternate beds of 

 coal, sandstone, and fireclay, formed for the most part in fresh- 

 water, and containing organic remains of terrestrial origin. And 

 2, the carboniferous or mountain limestone, which consists of 

 beds of purely marine origin ; with the remains of shells and 

 corals. In the mountain limestone of the South of Scotland, 

 however, beds of coal and shale are found associated with the 

 limestone. In most places where the coal measures appear, the 

 seams of coal present one characteristic feature, in having, as it is 

 called, an underclay. These underclays are coextensive with 

 every layer of coal, and consist of a tenacious clay, generally 

 called, " fireclay." They are characterized by the peculiar vegetable 

 stigmaria, to the exclusion of all other plants ; it is also an observ- 

 able fact, that while all other ferns, trees, etc., in the roof of the 

 coal are flattened, these stigmaria retain their natural forms, 

 branching freely. Since there is great importance attaching 

 itself to the right understanding of the nature of stigmaria, it will 

 be well before proceeding to give a short description of this, and 

 the other vegetables, from the remains of which coal is formed. 

 There are five hundred known forms of plants in the coal, which 

 all seem to point to the fact that the flora of the coal differs 

 widely from that which now prevails. Of these plants, the ferns 

 alone resemble those which now exist, and many of these, such as 

 the pecoptei'is and sphenopteris, are very similar to recent speci- 

 mens. About two hundred and fifty species of ferns have been 

 detected in the coal, a few of which seem to have been arborescent. 

 The vegetable which has been named Lepidodendron, was a kind 

 of tree, whose bark was covered with leaf scars. It appears 



